Characterization of Grating Out-Couplers in the Ultraviolet-C Wavelength Range for On-Chip Spectroscopy

On-chip optical spectroscopy has been applied from visible to mid-infrared wavelength, but not yet in the ultraviolet-C (UVC, λ = 200 – 280 nm) spectral region. Since most of the biomolecules exhibit strong absorption in the UVC, on-chip spectral analysis of their autofluorescence excited by an UVC pump is envisioned to be promising for healthcare applications. Here, we report the optical far-field characterization of the first grating out-coupler operating in the UVC region (λ = 266 nm). The simulated effective index of the fundamental mode propagating in the grating is in line with the retrieved experimental one.